Yuxing Sheng

Mechanisms of Cu2+ migration, recovery and detoxification in Cu2+-, SO42--containing wastewater treatment process with anaerobic granular sludge

In this study, anaerobic granular sludge with sulphate-reducing bacteria (SRB) was applied to treat Cu 2+-, -containing wastewater in an expanded granular sludge bed reactor. The migration and enrichment of copper in anaerobic granular sludge were envaluated. By analysing the sludge with X-ray diffraction, copper was determined to be present as covellite (CuS) in the sludge. Observations at the microscopic level showed that CuS precipitates were absorbed onto granules and gradually migrated from the outer to the interior layer of the granule over time and finally accumulated in the core of the granular sludge. Because of the migration of the CuS precipitates and the protection of the extracellular polymeric substances matrix, SRB were able to tolerate copper concentrations up to 10 mg/L. A copper removal efficiency of about 96% was observed at a steady state for 3 months, and copper was enriched in the granular sludge.

Effects of various pretreatments on biological sulfate reduction with waste activated sludge as electron donor and waste activated sludge diminution under biosulfidogenic condition.

The current study focused on the influences of various pretreatments, including alkaline, ultrasonic and thermal pretreatments on biological sulfate reduction with waste activated sludge (WAS) as sole electron donor. Our results showed that thermal and ultrasonic pretreatments increased the sulfate reduction percentage by 14.8% and 7.1%, respectively, compared with experiment with raw WAS, while alkaline pretreatment decreased the sulfate reduction percentage by 46%. By analyzing the WAS structure, particle size distribution, organic component, and enzyme activity after different pretreatments, we studied the effects of these pretreatments on WAS as well as on the mechanisms of how biological sulfate reduction was affected. The reduction of WAS and variation of WAS structure in the process of sulfate reduction were investigated. Our results showed that biosulfidogenesis was an efficient method of diminishing WAS, and various pretreatments could enhance the reduction efficiency of volatile solid in the WAS.

Analysis of a diverse bacterial community and degradation of organic compounds in a bioprocess for coking wastewater treatment

AbstractCoking wastewater is one of the most toxic industrial effluents since it contains high concentration of toxic organic compounds. Biological treatments are widely applied in coking wastewater treatment, pollutants can be degraded completely due to the synergistic effect of the community composition. In this study, the community structure and degradation of organic compounds of a full-scale coking wastewater treatment plant with anaerobic, anoxic, and oxic process (A1/A2/O) were studied. GC-MS results showed that phenols, indole, quinoline and pyridine, accounting for 61.70, 13.63, 7.71 and, 2.30%, respectively, were the main organic pollutants in the raw coking wastewater. Those pollutants were degraded gradually during the A1/A2/O bioprocess, respectively. High throughput pyrosequencing was applied to investigate the bacterial community, the sequences could be affiliated to 21 phylogenetic groups, including Proteobacteria, Chloroflexi, Bacteroidetes, Planctomycetes, Synergistetes, Chlorobi, Acidob...

Metagenomic insights into the microbiota profiles and bioaugmentation mechanism of organics removal in coal gasification wastewater in an anaerobic/anoxic/oxic system by methanol

Coal gasification wastewater is a typical high phenol-containing, toxic and refractory industrial wastewater. Here, lab-scale anaerobic-anoxic-oxic system was employed to treat real coal gasification wastewater, and methanol was added to oxic tank as the co-substrate to enhance the removal of refractory organic pollutants. The results showed that the average COD removal in oxic effluent increased from 24.9% to 36.0% by adding methanol, the total phenols concentration decreased from 54.4 to 44.9 mg/L. GC-MS analysis revealed that contents of phenolic components and polycyclic aromatic hydrocarbons (PAHs) were decreased compared to the control and their degradation intermediates were observed. Microbial community revealed that methanol increased the abundance of phenolics and PAHs degraders such as Comamonas, Burkholderia and Sphingopyxis. Moreover, functional analysis revealed the relative abundance of functional genes associated with toluene, benzoate and PAHs degradation pathways was higher than that of control based on KEGG database.

Current-induced four-state magnetization switching by spin-orbit torques in perpendicular ferromagnetic trilayers

We demonstrated current-induced four-state magnetization switching in a trilayer system using spin-orbit torques. The memory device contains two Co layers with different perpendicular magnetic anisotropy, separated by a spacer layer of Pt. Making use of the opposite spin current at the top and bottom surface of the middle Pt layer, magnetization of both Co layers can be switched oppositely by the spin-orbit torques with different critical switching currents. By changing the current pulse forms through the device, the four magnetic state memory was demonstrated. Our device provides an idea for the design of low power and high density spin-orbit torque devices.

The synergistic effect of organic foulants and their fouling behavior on the nanofiltration separation to multivalent ions

AbstractThis work aimed to determine the effect of organic foulants and fouling behavior on separation of multi-ions for nanofiltration (NF) membrane. Three model organic foulants (bovine serum albumin, lysozyme, and humic acid) were selected and studied in depth. The rejections of mono- and di-anions by virgin membrane varied with different organic foulants because of foulant-enhanced co-ion competition. Subsequent multi-ions separations by fouled membranes were different due to the zeta potential and structure of the fouling cake. In contrast to the single protein system, Cl− and rejection was reduced by HA fouled membrane. However, with added proteins in the HA solution, mixed systems experienced decreasing Cl− rejection and increasing rejection. In addition, solution chemistry (solution pH, ionic strength, and Ca2+) had marked effect on the cake layer composition, likely due to the changing interaction between foulant and foulant, as well as between foulant and NF membrane. The suitable foulant cake s...

Novel technique for internal structure and elemental distribution analyses of granular sludge from reactors for wastewater treatment

A novel technique for internal structure and elemental distribution analyses of granular sludge is presented. Sludge samples were freeze-dried and embedded in epoxy resin to form a module, which were then ground and polished to obtain sequential cross-sections. The cross-sections were analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). SEM observations showed that one granule was formed having several cores with different inorganic minerals, rather than a single core. EDX results indicate that the main elements of the granules are O, Ca, Mg, and P. In addition, the distribution areas of calcium and magnesium in the granule do not coincide.

Characteristic of single/mixed organic foulants on nanofiltration membrane and prompt fouling predictor method

AbstractThe fouling behavior of nanofiltration (NF) membranes by proteins bovine serum album (BSA), lysozyme (LYS), and humic acids (HA), as well as their mixtures was studied in a cross flow bench-scale cell. The similarities and differences of the effects of pH on single and mixed organic foulant systems were compared by analyzing the size distribution and zeta potential of foulants in the feed, and in conjunction with the characterization of fouled NF membranes, respectively. Results showed that the fouling behaviors of both single and the mixed systems were significantly correlative with solution pH, moreover BSA/LYS combined with HA appeared more aggravated fouling behavior than single foulant within the test pH range. For solution pH, this can affect interactions of foulants–foulants and foulants–membrane by changing zeta potential of them. Also, therefore, zeta potential value could be used to predict the fouling behavior of NF. Considering the experimental results, more severe fouling behavior by ...